The present application claims priority under 35 U.S.C. xc2xa7119 to Japanese Patent Application No. 10-334,822, filed Nov. 25, 1998, entitled xe2x80x9cMethod And Apparatus For Manufacturing Prepreg.xe2x80x9d The contents of that application are incorporated herein by reference in their entirety.
1. Field of the Invention
The present invention relates to a method and an apparatus for manufacturing a prepreg, in which the prepreg is made of a fibrous reinforcing substrate coated and impregnated with a thermosetting matrix.
2. Description of Background Information
Japanese Laid-Open Patent Application No. HEI 8-281645 discloses a technique for continuously manufacturing a prepreg by allowing a long sheet-shape fibrous reinforcing substrate to be coated and impregnated with a thermosetting matrix resin containing no solvent while the reinforcing substrate travels.
In detail, this technique shows a prepreg manufacturing method which includes a first coating process for applying a thermosetting matrix resin containing no solvent in a molten state onto one surface of a sheet-shape reinforcing substrate by using a die coater, a process for heating the reinforcing substrate coated with the thermosetting matrix resin by a heating unit of a non-contact type so that the reinforcing material is impregnated with a thermosetting matrix resin, a second coating process for applying a thermosetting matrix resin to the reinforcing substrate impregnated with the thermosetting matrix resin on its surface opposite to the resin-coated surface by the first coating process by using a die coater, and a process for heating the reinforcing substrate coated and impregnated with the thermosetting matrix resin by a heating unit of a non-contact type so as to semi-cure the thermosetting matrix resin to form a sheet-shape prepreg.
However there are some problems in this technique. That is, since a die coater is used to apply the thermosetting matrix resin onto the reinforcing substrate, the thermosetting matrix resin tends to easily adhere to the inside of the die coater. Accordingly, the coating precision deteriorates and long time is required to clean and maintain the die coater. Moreover, although a die coater itself is very expensive device, it is necessary that two die coaters are respectively placed on one surface and on another surface of the reinforcing substrate so as to apply the thermosetting matrix resin on the respective surfaces. As a result, equipment costs are high. Furthermore, since the thermosetting matrix resin is applied to the both surfaces of the reinforcing substrate, air inside the reinforcing material tends to be entrapped by the matrix resin. Accordingly, voids are likely to occur in the prepreg.
It is an object of the present invention to provide a method and an apparatus for manufacturing a prepreg in which a prepreg is manufactured without causing many tasks for cleaning and maintaining the apparatus.
Another object of the present invention is to provide a method and an apparatus for manufacturing a prepreg in which the equipment costs is reduced.
Yet another object of the present invention is to provide a method and an apparatus for manufacturing a prepreg in which generation of voids is prevented.
The object is achieved according to the present invention by providing a novel method for manufacturing a prepreg in which a reinforcing substrate is impregnated with a thermosetting matrix resin. In the method, the reinforcing substrate is moved in a traveling direction. The thermosetting matrix resin is supplied to an outer circumferential surface of a transferring roller. The thermosetting matrix resin which substantially contains no solvent and which is in a molten state is transferred from the outer circumferential surface of the transferring roller to a first surface of a reinforcing substrate while the reinforcing substrate moves. The thermosetting matrix resin which is transferred to the first surface is forced to permeate through the reinforcing substrate by pressing at least one pressing roller on the thermosetting matrix resin transferred to the first surface while the reinforcing substrate moves. The reinforcing substrate impregnated with the thermosetting matrix resin is heated to semi-cure the thermosetting matrix resin.
According to the method of the present invention, the application of the thermosetting matrix resin onto the reinforcing substrate can be carried out by transferring by using the transferring roller, it is not necessary to take so many tasks in cleaning and maintenance. In addition, equipment costs for manufacturing prepreg can be lowered because the transferring roller is inexpensive as compared with the die coaters. Moreover, the thermosetting matrix resin transferred to the first surface of the reinforcing substrate is forced to permeate through the reinforcing substrate to the second surface thereof by using the pressing roller. Namely, both surfaces and the inside of the reinforcing substrate are coated and impregnated with the thermosetting matrix resin simply by transferring the thermosetting matrix resin to the first surface of the reinforcing substrate by using the transferring roller and then pressing the pressing roller thereon. Thus, it is not necessary to respectively arrange two separate application devices for applying both surfaces of the reinforcing substrate such as the conventional method of using two die coaters arranged in the both side of the reinforcing substrate. Therefore the equipment costs can be further reduced. Furthermore, since air inside the reinforcing substrate easily escapes from the second surface thereof without being entrapped therein by the matrix resin, the generation of voids on the obtained prepreg can be prevented.
In the present invention, a heating device, which is for heating the thermosetting matrix resin transferred to the reinforcing substrate, may be placed on the side of the second surface of the reinforcing substrate in a non-contact manner. With heating the transferred thermosetting matrix resin on the reinforcing substrate by the heating device, the thermosetting matrix resin can be kept in such an desirable molten state as not to lower its viscosity, thereby promoting the thermosetting matrix resin to permeate into the reinforcing substrate. As a result, thermosetting matrix resin permeates the reinforcing substrate well.
Optionally a plurality of the pressing rollers may be arranged along the advancing direction of the reinforcing substrate. In this case, since the thermosetting matrix resin transferred to the first surface of the reinforcing substrate can be pressed plural times by the respective pressing rollers to permeate through the reinforcing substrate to the second surface of the reinforcing substrate, it is possible to control the amount of permeation of the thermosetting matrix resin more precisely.
Optionally, a backup sheet having mold release characteristics with respect to the thermosetting matrix resin may be arranged in a position of confronting with the pressing roller in such a manner as to contact the second surface of the reinforcing substrate. In this case, the thermosetting. matrix resin can be allowed to spread on the second surface of the reinforcing substrate by utilizing the surface tension of the backup sheet, thereby making it possible to uniformly apply and spread the thermosetting matrix resin on the second surface of the reinforcing substrate and consequently to increase the amount of application and spread thereof.
Optionally, air pressure in the side of the second surface of the reinforcing substrate may be reduced. In this case, the thermosetting matrix resin transferred on the first surface of the reinforcing substrate can be allowed to easily permeate through the reinforcing substrate to the second surface thereof because of pressure difference occurring between the first surface and the second surface of the reinforcing substrate. Therefore, the rate of permeation of the thermosetting matrix resin by the pressing roller can be increased as well as the amount of application and spread can be increased.
Optionally, the pressing roller may be rotated in a reversed direction against the traveling direction of the reinforcing substrate. In this case, the thermosetting matrix resin in a molten state transferred on the first surface of the reinforcing substrate is subjected to a rubbing action against the reinforcing substrate by pressure from the pressing roller. Therefore, by adjusting the rotation speed of the pressing roller, the amount of permeation of the thermosetting matrix resin can be easily controlled.
Optionally, the pressing roller may be rotated in the same direction as the advancing direction of the reinforcing substrate. In this case, by adjusting a winding angle of the reinforcing substrate against the pressing roller, it becomes possible to easily control the amount of permeation of the thermosetting matrix resin.
Optionally, a wiping roller shifting the reinforcing substrate so as to wrap the reinforcing substrate around the transferring roller may be installed. In this case, the thermosetting matrix resin on the surface of the transferring roller can be wiped out with the reinforcing substrate wound around the transferring roller by the wiping roller, thereby making it possible to prevent the thermosetting matrix resin from adhering on the surface of the transferring roller in the event of some troubles such as a temporary stoppage of the transferring roller.
Further, the object is achieved according to the present invention by providing a novel apparatus for manufacturing a prepreg which includes a feeder, a transferring roller, a resin supplier, at least one pressing roller and a heater. The feeder is configured to feed a fibrous reinforcing substrate which has a long sheet-shape and travels in the apparatus. The transferring roller is configured to transfer a thermosetting matrix resin in a molten state which is supplied to an outer circumferential surface of the transferring roller onto a first surface of the reinforcing substrate. The resin supplier is configured to supply the thermosetting matrix resin to the outer circumferential surface of the transferring roller. The at least one pressing roller is configured to force the thermosetting matrix resin which is transferred to the first surface to permeate through the reinforcing substrate by pressing the at least one pressing roller on the thermosetting matrix resin transferred to the first surface. The heater is configured to heat the reinforcing substrate impregnated with the thermosetting matrix resin to semi-cure the thermosetting matrix resin.
Optionally, in the apparatus, an accumulator being operated upon switching the reinforcing substrate over may be employed.
Optionally, in the apparatus, a resin gun for supplying the thermosetting matrix resin in a molten state onto the transferring roller may be employed. In this time, for a sake of feeding the thermosetting matrix resin containing no solvent into the resin gun, a resin feeder may be employed.
Optionally, in the apparatus, in the apparatus, a metering roller for uniformly spreading the thermosetting matrix resin in a molten state on the surface of the transferring roller may be employed.
Optionally, in the apparatus, a back-up roller for pressing the reinforcing substrate onto the transferring roller may be employed.
Other objects, features and advantages of the present invention may be ascertained by reviewing the present disclosure and the accompanying drawings.